Newton, Leibnitz, and Boscovich to the Atomic Theory. 77 



light, must be very small compared with that of hydrogen, and small 

 when compared with that of vapour or nitrogen. In other words, its re- 

 fractive and reflective power must be very low. (c) From being merely 

 an equatorial form whoUy wanting in polar parts, it must tend to unite 

 with almost every substance ; for it can scarce be so bad in reference to 

 the law of sphericity as when existing alone. It wiU, therefore, be 

 parasitic in a high degree, and (in consequence of its low reflective 

 power), it wLU be destructive of the lustre of other bodies. It will, 

 therefore, be a corrosive substance, {d) When no other bodies are 

 presented to it for union, its own particles will 

 unite among themselves and go in couples (as 

 in this figm'e) ; for of such a couple the atmo- 

 sphere may be spherical, though of a single 

 particle it carmot, at least with the same faci- 

 lity. In this coupled state, therefore, it wiU 

 also be less active than when existing in single 

 atoms. This species may, therefore, be ex- 

 pected to be known in two states of existence, 

 one much more active than the other, (e) 



When existing permanently in the aeriform state, there can be no 

 doubt that it wiU exist in coupled atoms. The volume of such coupled 

 atom, therefore, under the law of assimilation, being assimilated to the 

 volume of a single atom of hydrogen, of vapour, or of nitrogen, it 

 will weigh double what the atomic weight would indicate, and half 

 a volume of this kind of gas will be equivalent to a whole volume 

 of the other sorts. Thus the genetic equivalents of a volume of 

 vapour must be one volume of hydrogen, and half a volume of this 

 species; and the spec. grav. of hydrogen being '0693, of vapour '623, of 

 nitrogen -970, that of this species must be 1-109. Now, in all these 

 respects, this new species represents oxygen. 



And thus we find vapour to be dimorphous in a very beautiful manner. 

 In union with a molecule of the pental or pentagonal series of forms, 

 such as nitrogen, it can only exist as HO. But 

 let it be disengaged from such union, and go free, 

 or let it unite with H, or any other molecules 

 of what may be called the trinal or trigonal 

 series, and it relapses into a q, the properties of 

 which cannot but be very different from those of 

 H 0. And, indeed, in H O, this primordial 

 species, have we not the index and type of the 

 three great classes of chemical properties, the 

 acid represented by H outstanding on the pole of a molecule, tlic basic 



